Accurate control over the tension applied to threaded fasteners for machinery is of increasing importance in assembly operations. Various devices have been utilized in fastener tightening power tools to shut off the power supply or disengage the power tool from the fastener at a predetermined torque output. The resulting tension produced in the fastener, however, has not been within the required tolerances for maximum fastener utilization. Several methods have been developed which improve tensioning accuracy, such as, the so-called "turn of the nut" or "constant energy application" method. In U.S. patent application, Ser. No. 601,441, of which I am a co-inventor, several methods of fastener tensioning and inspection are described, which are capable of producing a relatively accurate tension level within the fastener, and simultaneously detect common fastener faults, such as, cross threading, thread stripping, defective bolt, etc. One of the methods described in the above-referenced patent application includes the steps necessary to detect the point at which a bolt begins to yield; that is, when the increase in the torque is no longer proportional to the increase in rotation. The power tool is shut off in response to the yield point detection; the shut off occurring within a predetermined range of a second parameter chosen to serve as a inspection method. In the above method, yield point of the fastener is precisely determined and must fall within a predetermined range as a inspection method.